Automatic bump mapping
As far as I see, if normal is positive light colours bump outwards and dark inwards, if negative - the other way round.

The rest doesn't seem easy, but here are some links. I think "Method" is mostly about quality:
http://kishalmi.servus.at/3D/bumpcode/

"Space" should tell in which space the normal vector will be stored. But the results look strange.

Anyway - why not use cycles?